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By M. E. Karabin, R. J. O'Malley

"A mathematical model of the roll casting process has been developed which predicts macro-variables, such as roll separating force, roll torque, and strip exit speed for a range of roll speeds. Continuum variables, such as interface pressure, interface shear stress, freeze-front shape, and internal temperature distribution are also predicted.The model consists of two independent segments: solidification and rolling. The solidification model is two-dimensional (thickness and rolling direction) and is capable of handling alloy solidification. The solidification model is employed until solidification through the thickness is complete, then the rolling solution is activated.The rolling model is a one-dimensional (rolling direction) mechanical solution based on the von Karman approach, coupled with a two-dimensional thermal solution. The flow stress is expressed as a function of the average through-thickness temperature of the strip.Experiments were performed using a laboratory roll caster to test and refine the model. Experimental strip exit temperatures were used as input to the model. Experimental and predicted roll torque and strip exit speea were forced into agreement at a single reference roll speed to obtain values for the coefficient of friction and the interfacial heat transfer coefficient. Using these values, good agreement was obtained between predicted and experimental torque and strip exit speed over the entire range of roll speeds examined."

Jan 1, 1986

By J. Antrekowitsch

Keywords: residues, fluorides, chlorides, zinc, steel mill dust The recyclability of various nonferrous metal wastes often suffers from a relatively high fluorine and chlorine content. Both are inserted in most cases by the use of plastic contaminated scrap and a wide variety of different coatings. These halogens lead to poor product qualities and off gas contamination. Especially the history of zinc recovery from steel mill dusts shows, that the today common hydrometallurgical options are on their limit and therefore are not sufficient in most cases. This thermochemical study should give more information about different pyrometallurgical options, that offer both a chlorine and fluorine reduction and efficient zinc recovery, preferably in one process step. Selective evaporation in different atmospheres and conversion with the use of hydrogen are the main parts in this study. The results combined with the relatively small information available from literature should provide a basis for further investigations in this field.

Jan 1, 2005

By S. Gopalan, J. D. Milshtein, S. N. Basu

Production of syngas is proposed utilizing the W/W03 redox system and employing a solarpowered two-step thermochemical cycle. Three chemical reactions occur in two chambers. Assisted by a solar concentrator, a high temperature reaction reduces W03 powder to metallic tungsten in both chambers. Subsequently, the temperature in one of the chambers is lowered and H2(g) is produced via re-oxidation of the tungsten powder using steam. The temperature in the other chamber is simultaneously lowered to an intermediate temperature and CO(g) is produced via oxidation of the tungsten powder using C02(g)· The gas streams coming out of the two chambers result in the syngas production. A complete thermodynamic analysis of the system is described. The W/W03 redox cycle offers greater gravimetric fuel productivity compared to previously proposed systems, and the entire cycle can be operated below 1273K.

Jan 1, 2013

By Chuang Y-Y

A summary is made on the thermodynamic analysis for two of the four ternary systems of the quaternary Cu-Fe-Ni-S. The analysis is being extended to ternary Cu-Fe-S and then to the quaternary. An analysis is already made for the metal ternary but is not reported here. Experiment is being carried out to measure the liquidus surface. of Fe-Ni-S equilbrium with the fcc solid solutions of (Fe, Ni). The presentation at the Symposium will include all the results obtained at the time of presentation.

Jan 1, 1983

By Jillian Spindura

This work investigates the carbothermic reduction of the complex sulphide mineral, pentlandite, in the presence of lime. The effects of change in temperature and the use of different carbon sources are studied and the role of these variables on the reducibility of pentlandite mineral is discussed. The microstructures of the heat-treated pellets are examined using X-ray diffraction and scanning electron microscopic techniques. The latter analytical method also allows any variation in the morphology and composition of the metallic phases formed, with temperature, to be considered. The kinetics of the reduction process is studied and the magnitude of the overall activation energy is determined from the plots of percentage reduction versus time.

Jan 1, 1996

By Pengfu Tan

A thermodynamic model has been developed to predict the distribution behaviors of Cu, Fe, S, O, Pb, Zn, As, and heat balance in a lead blast furnace. The modeling results have been validated by the plant data of a lead smelter in Asia. The model can be used to predict for any set of controllable process parameters such as feed composition, smelting temperature, degree of oxygen enrichment and volume of oxygen-enriched air. The effects of the blast air, industrial oxygen, and coke charge on the distributions of Cu, Fe, S, O, Pb, Zn, As, and heat balance, and on the lead loss in slag have been presented and discussed.

Jan 1, 2005

By Alhondra de los Santos, Jesús L. Valenzuela, Jose R. Parga

"The present study evaluated the feasibility of using iron species generated by electrocoagulation (EC) as an adsorbent for removal As(III/As(V) from aqueous media. The full potential of EC was evident in that more than 99 percent of arsenic was removed without addition of chemical reagents. The adsorbent iron-species generated by EC was characterized by Chemical Analyses, X-Ray Diffraction and Scanning Electron Microscopy. The experimental data were correlated by employing a Langmuir adsorption isotherm. Thermodynamic parameters such as ?H o , ?S o and ?Go were calculated. The adsorption process was found to be exothermic and spontaneous.1. IntroductionArsenic contamination in potable water supplies is a serious health problem in many countries around the world. Groundwater arsenic contamination in La Comarca Lagunera Mexico was first reported 30 years ago [1]. Arsenic concentration has been found in well water from several communities ranging from 0.25 to 1.0 ppm. The elevated concentration of arsenic in water, above that originating from natural sources, has been attributed to the use of organoarsenical pesticides in the cotton fields and also to the millions of tons of waste slag generated at a local lead smelter [1]. The main arsenic species present in natural waters are arsenate ions 3- 4 AsO (oxidation state V) and arsenic ions H3AsO3, - 2 3 H AsO and 2- 3 HAsO oxidation state III). However, As(V) ions are most prevalent in oxygenated water while As(III) is found for anaerobic conditions, such as in well water or in groundwater. Conventional methods of arsenic removal rely on chemical-based treatment with lime, alum coagulation, iron coagulation and chemical oxidation. Other processes used with varying degrees of success include adsorption onto activated carbon, reverse osmosis, nanofiltration, manganese dioxide, magnetite and ionexchange resins [1-3]. These conventional processes generate a considerable quantity of secondary hazardous waste such as solid sludge, which also pose serious environmental problems. These drawbacks have forced various industries to search for effective, alternative treatment technologies for arsenic with a preference for electrochemical methods."

Jan 1, 2008

By Jeffrey R. Taylor

The distribution of low concentrations of Cr, Mn, Rh, Co, Ni, Ag and Fe between copper matte and bullion phases has been measured at 1200oC. These results. together with values for nine other elements, have been used to develop a simple model to describe the distributions in terms of known thermodynamic properties?. The Temkin model for ionic melts was assumed to apply to the sulphide species in the Cu-S matte? phase and it is shown that the choice of sulphide species is particularly important for successful representation of the experimental .results?. In general, the lowest sulphlde (minimum sulphur :. metal ratio)? formed by the. metal is most suitable, although Ni, Co, Rh and Pd appear to associate with more sulphur in the melt than suggested by the? composition of their lowest sulphide. A correlation between the composition of the metal sulphide species formed in the ternary system and the? position of the minimum in the free energy of mixing curve in the metal-sulphur binary -system is? proposed.

Jan 1, 1983

By Staia. Mariana H.

Thermochemical equilibria of the heterogeneous system Ti-N-H-CI-Fe-Cr-Mo-Ni-Mn-C were calculated by using a commercial software based on the minimization of the free energy. Equilibrium calculations were done for temperatures varying between 800" and l 100°C and an initial molar relationship between reactants, a=NJTiCI,, of 0.1 to 2. The deposition process was considered to occur at atmospheric pressure. The activities of the alloying elements of the stainless steel were considered equal to their molar fractions. It was shown that for the conditions studied the substrate is no inert with respect to the gaseous phase. The existence of liquid chlorides was predicted for temperatures between 800" and 850°C and a ratio between 0.3 and 0.9. The most important metallic chlorides which appears to be present from the calculations in appreciable quantities in the gaseous phase are iron dichloride and manganese dichloride. In the low-temperatures zone and for low initial nitrogen contents, it result that the appearance of the liquid chlorides seems that partially inhibits the production of gaseous HCI. The highest deposition process efficiency calculated is obtained at a temperature 2 900°C and a N2/TiCI, ratios 2 0.7.

Jan 1, 1995

By Varadajan Seshadri

The increase in production of continuous casting machines requires long ladle sequences without interruption. Very often the production schedule has to accommodate a variety of steel grades. In such cases downgrading may be inevitable. Models must be made available to study the alternatives that would make possible mixing of steels in the tundish but minimizing the losses due to downgrading the slabs. Physical modeling was used to evaluate the influence of variables such as internal geometry of the tundish, presence of turbulence inhibitors, depth of ladle long nozzle, weight of steel in the tundish, steel throughput upon the tundish transition curve. Expressions for minimum residence time and transition period have been determined. Mixing-transition is allowed to continue inside the liquid pool in the mold and the final solute distribution in a given cross section is captured by a solidification model. The result is a map of the transition in the final product.

Jan 1, 2006

By A. Deneys

An experimental technique has been devised for studying the reaction kinetics of the reaction: ZnO + 2Fe0 = Zn(g) + Fe203, by which zinc evolution can occur from a molten slag bath in the absence of a carbonaceous reductant. When studying the reaction kinetics by heating from room temperature, solid state reactions and poorly defined melting points may obscure the starting point of the reaction. In order to eliminate this problem, an experimental technique was devised whereby two molten slags could be melted independently, and then mixed, to provide a well defined starting point from which to begin taking measurements. Two crucibles were mounted in a vertical reaction cylinder. The upper, mild steel, crucible had a bottom pouring plug which was sealed by a steel stopper rod. A fayalite mixture was contained in this crucible. The lower crucible contained an A12O3-CaO-SiO2-ZnO solution. Once the two slags had been melted, the steel stopper rod was removed from the upper crucible. The upper, reduced slag (fayalite in equilibrium with the upper steel crucible), drained into the lower crucible where the two slags were mixed by submerged argon stirring. Dip samples were taken to measure the zinc content of the final mixture as a function of time. The experimental procedure will be described, as well as results of experiments which were conducted on synthetic slags. The system investigated was similar to the lead blast furnace slag which is produced by the primary lead smelters of Missouri, USA.

Jan 1, 1997

By W. Song, C. Richards, B. Q. Li

"This paper presents a two-phase flow numerical model for spouting gas-particle flow reactors used in chemical vapor deposition processes for manufacturing heart valves and other biomedical implants. The model is developed based on the Eulerian-Eulerian formulation of gas-particle flows, with the k-e engineering model modified with the presence of particles for the description of turbulent gas flows. In parallel with the numerical model development, physical models are set up, where the particle image velocimetry is used for visualizing the particle flows and spout shapes and heights and optical probes are used to measure the particle velocities. The numerical model predictions are compared reasonably well with the experimental measurements.IntroductionVarious biomedical implant components, such as bone joints, dental components and heart valves, are coated with bio-compatible thin films by chemical vapor deposition in particle-laden chemical reactors [l-5]. In these reactors fine particles are used as packing and supporting media. During the coating operation, these packed particles are fluidized by an upward gas jet from the nozzle, reach a certain height and fall back on the top of an annulus region. These recirculating particles are mainly for levitating the implant components (usually one or two in a reactor at one time) so that every portion of them is equally exposed to the gaseous atmosphere. An equal exposure is critical for forming a uniform, mechanically strong and corrosion-resistant coating on implants. Plant experience shows that the quality of the coating is directly related to a stream of operating parameters such as temperature, particle size and loading, and gas flow rates [6]. Optimization of these operating parameters for improved reactor performance depends crucially upon our fundamental understanding of the physics governing the gas-particle flow, heat, and mass transfer phenomena taking place in these reactors."

Jan 1, 2004

By Robert De Saro, Willis Bateman, Ramesh Jain

A Vertical Floatation Melter (VFM) has been developed (sponsored by DOE) which simultaneously decoats and melts organic laden scrap in a single unit. Scrap aluminum is fed into the top of the VFM where it falls through a cone. Hot gases flow upwards through the cone, imposing a variable drag force on the scrap. Equilibrium is reached in which the scrap weight equals the drag force and the scrap becomes suspended. The gases strip off and vaporize the organics. Next, the scrap reaches a liquid state, taking on a more aerodynamic teardrop shape, allowing it to fall into a holding furnace. Heat transfer coefficients are 10 times higher than that of a conventional furnace, allowing rapid melting at a low gas temperature. Typical energy use is well under 2,324 joules/g (1,000 Btu/lbm) with a metal yield from 92 to 98%. This paper reports on the operation and data of a 453 kg/hr (1,000 pph) pilot-scale VFM.

Jan 1, 2000

By Dan Mancuso

This case study is an example of how Encyle/Texas, Inc. (a subsidiary of ASARCO) responded to various socio-economic forces by converting an idle zinc hydrometallurgical refinery into a metals recycling facility. The facility accepts metal-laden process waste streams and produces various "synthetic ores" which are sold back to industry. Acceptance and reactions by industrial, political, economical and regulatory interests towards the project are also discussed.

Jan 1, 1992

By F. Mucciardi

With the increasing trend to continuous smelting and converting, granulation of copper matte is gaining prominence as a means of decoupling the smelting and converting operations. Moreover, granulation is also being seen as a possible avenue to using higher grade oxygen in converters. By feeding cold solid matte, the oxygen concentration can be increased to compensate for the lower enthalpy feed. This leads to a higher grade of SO2 in the off gas and a lower total flow rate. Current granulation technology relies on the cooling of a falling matte film by water jets. This technology while effective has several drawbacks including those related to safety. Noranda and McGill University have developed a new process (patent pending) for solidifying copper matte (or slag). It overcomes many of the negatives of current technology. The system is based on an air cooled twin roll caster. This: new system uses no water and instead incorporates heat pipe technology to transfer the heat from the solidifying matte to the cooling air to produce a thin strip of 1 to 2 mm in thickness. Testing of a prototype unit demonstrated its viability. This paper describes this newly developed, twin roll casting system that is completely waterless. The advantages of this process as well as the findings from several tests are also detailed.

Jan 1, 1999

By Tianyou Huang, Yuan Lu, Haimin Long, Jinwu Kang, Gang Nie

"The distortion of metal parts during heat treatment process is one of the main obstacles in industry to ensure high-quality work and less or no machining allowance, especially for large but thin steel castings such as heavy turbine blades. In the paper, a method is proposed to control the distortion by adjusting heat transfer coefficient of metal parts during heat treatment process. Required heat transfer coefficients can be realized by getting the metal parts into contact with various media such as water spray, insulation felt or materials with different heat conductivity. The control method based on this idea is set up and achieved. By using insulation felt and water spray to change the heat transfer coefficient during the stages of heat treatment process, the results indicate that the proper control time and vary with materials.IntroductionThe distortion of metal parts during heat treatment process is one of the main obstacles in industry to ensure high-quality work and to realize less or no machining allowance [1]. For example, the Three Gorges turbine blade’s distortion is as large as 50mm during heat treatment process. The uneven heating and cooling during heat treatment process is the main reason for distortion [2]. By adjusting heat transfer coefficient of different areas of metal parts, the heat treatment process could be controlled. The temperature variation, direct cause for distortion, could be under control. Loeser Klaus used high pressure gas to achieve uniform heat transfer during gas quenching and proposed the possibility to use ""Dynamic Quenching"" processes where the quenching severity is varied during quenching by stepwise control of either gas velocity or gas pressure [3]. Li Zhichao also suggested minimizing distortion by marking a component into several areas and imposing different heat transfer coefficients on each area [4]. Heat transfer coefficient can be controlled by getting the metal parts into contact with different media such as water spray, insulation felt, air or different heat conduction materials. In addition, the exact time to adjust the heat transfer coefficient is another factor for distortion. A method is presented in this paper by actively adjusting heat transfer coefficient for different areas of metal parts and different stages of heat treatment process to control their distortion. The corresponding experiments have been made by using different metal materials."

Jan 1, 2012

By M. Friák, L. G. Wang, M. Šob, V. Vitek

"The paper gives an account of applications of quantum-mechanical (first-principles) electronic structure calculations to the problem of theoretical tensile strength in metals and intermetallics. First, we briefly describe the way of simulating the tensile test and the electronic structure calculational method. Our approach is then illustrated on calculations of theoretical tensile strength in W, NiAl and transition metal disilicides MoSi2 and WSi2 with C11b structure. In Wand NiAl, we consider uniaxial tension along [001] and [111] directions. Although tungsten is elastically nearly isotropic (C44 = C”), theoretical tensile strength exhibits a marked anisotropy (oth/001 = 29 GPa, o'th/111 = 40 GPa). Calculated results compare favorably with experimental value of 24.7±3.6 GPa obtained for tungsten whiskers grown along the [110] direction. Similarly, in NiAl, the 'hard' orientation [001] differs very significantly from the [ill] orientation (oth/001 = 46 GPa, oth/111 = 25 GPa). This anisotropy is explained in terms of higher-symmetry structures present or absent on the calculated deformation paths. In disilicides, the theoretical strength is calculated for [001] loading (oth/001 = 37 GPa and 38 GPa for MoSi2 and WSi2 , respectively). The role of relaxation of internal structure parameter is discussed and changes in bonding conditions during the tensile test are analyzed.IntroductionIn most engineering applications, the strength of materials is limited by the presence of internal defects. If there were no defects, then, for example, the tensile strength could be several orders of magnitude higher and its value would be comparable with that of shear modulus. Therefore, the strength of ideal (defect-free) crystal represents an upper limit of attainable stresses, which is called the ideal strength. While it may not be possible to achieve the ideal strength in practice, it is not possible to exceed it. However, the ideal strength is already approached in situations which are technologically relevant. These include the low-temperature deformation of inherently strong materials, such as diamond, Si, Ge and some of the transition-metal carbonitrides, deformation of whiskers, nanoindentation of materials with low defect densities, hardened thin films and coatings etc. The ideal strength sets the limits of elastic stability of a solid. Its knowledge is useful for estimation of the ideal work of fracture stresses needed for homogeneous nucleation of dislocations and for modelling of crack propagation."

Jan 1, 2001

By Jamil M. Khalifeh, Shadia J. Ikhmayies, Bothina A. Hamad

"We computed the optical properties of the cubic niobium nitride (o-NbN) compound using the full potential linearized augmented plane wave (FL-LAPW) method within density functional theory (DFT). The complex dielectric function and optical constants, such as optical absorption coefficient, refractive index, extinction coefficient, energy-loss spectrum, and reflectivity, are all calculated and compared with experimental results. The behavior of the computed quantities is similar to that obtained experimentally, but the optical positions are shifted to lower energies. This shift was related to the strong interband transitions, which are located at energies higher than 5 eV for NbN- as they are for IV B transition-metal mononitrides- and they appear in the computed spectra and not in the experimental spectra. These interband transitions simply shift the position of the reflectivity edge or the screened plasma frequency to the longer wavelength side.IntroductionIn recent years, NbN, as a transition metal nitride, has become a very popular material due to its high hardness, melting point, wear resistance, chemical inertness and temperature stability, which makes it suitable for use as emission cathodes in microelectronics and sensors, optical films and micro-mechanics etc [l]. Niobium nitride has long been known as highly polymorphic material, for which several crystalline structures have been reported in the literature [2]. These structures include the well known super-conducting rock-salt (Fm-3m, or Bl) structure (o-NbN), the hexagonal structure with space group p63/mmc and prototype Fe2N (18fuN), the hexagonalstructure with space group p63/mmc and prototype NiAs ~-NbN) and others.There has been a lot of computational studies for the structural and electronic properties ofNbN [3, 4-7], but according to our knowledge there is not any computational work that has been devoted to study the optical properties of this transition metal compound. At the same time a number of authors had performed experimental work in this direction. For example, Xin-kang et. al [l] studied the microstructure and optical properties of magnetron sputtered NbN thin films. Torche et. al [8] studied the composition, structure, electrical and optical properties of nonstoichiometric niobium nitrides. Newport et. al [9] investigated the reflection and transmission spectra of cubic niobium nitride films, and Tanabe et. al [10] had investigated the optical parameters and reflectivity of reactively sputtered NbN thin films by using in situ ellipsometry."

Jan 1, 2013

By I. Gaballah

About forty percent of the SOx emissions are generated during the processing of metal sulfides of Cu, Pb, Zn, Ni, etc. Although new technologies for metal sulfide's smelting allow the production of H2S04 with a reasonable cost and decrease the emissions of sulfur oxides, the generated quantity of SOx is considered as a serious threat to environment. This paper suggests alternatives for low temperature processing of complex sulfide ores or concentrates 'CSO or CSC' under neutral, reducing and chlorinating atmospheres or their combination. At T > 400 "C, The neutral and reducing treatments allow the decomposition of pyrite and the partial recovery of sulfur as So and H2S. At 300 "C, the chlorinating treatment of CSC is fast, exothermic and allows the separation of FeC13 from the valuable elements' chlorides. It also generates SyCIx that can be either reduced by H2 or hydrolyzed in presence of sodium sulfide. The recovery rate of elemental sulfur with respect to the sulfur input exceeds 90 %.

Jan 1, 1999

By Md Sazzadur Rahman

Electrochemical Impedance Spectroscopy studies were conducted on two organic thermal energy storage materials; Neopentylglycol (NPG) and 2-Amino-2-Methyl-1,3-Propanediol (AMPL). The ionic conductivities and dielectric relaxation times in the low temperature ordered a-phase (monoclinic for both NPG and AMPL) as well as high temperature orientationally disordered cubic y-phase are reported.

Jan 1, 2006